Cantopotamon hengqinense Huang, Ahyong & Shih, 2017

Huang, Chao, Wong, Kai Chin & Ahyong, Shane T., 2018, The freshwater crabs of Macau, with the description of a new species of Nanhaipotamon Bott, 1968 and the redescription of Nanhaipotamonwupingense Cheng, Yang, Zhong & Li, 2003 (Crustacea, Decapoda, Potamidae), ZooKeys 810, pp. 91-111 : 92

Cantopotamon hengqinense Huang, Ahyong & Shih, 2017 Fig. 2C

Cantopotamon hengqinense Huang, Ahyong & Shih, 2017: 9, fig. 5.

Type material.

Holotype: SYSBM 001558, male (19.9 × 16.0 mm), Dahengqin Mountain (22.11N, 113.50E), Hengqin Island, Zhuhai City, Guangdong, China, small hillstream, under rocks, coll. C. Huang, February 2016. Paratypes: SYSBM 001559, 1 female (13.0 × 10.6 mm), same data as holotype. SYSBM 001560-001561, 2 males (15.5 × 12.4 mm, 13.2 × 10.7 mm), same data as holotype.

Other material examined.

China: IACM, 2 males (20.5 × 16.5 mm, 19.5 × 16.5 mm), Coloane (22.12N, 113.56E), Macau, small hillstream, under rocks, coll. K.C. Wong, November 2009. SYSBM 001640, 1 male (17.5 × 13.6 mm), Dahengqin Mountain, Hengqin Island, Zhuhai City, Guangdong, small hillstream, under rocks, coll. C. Huang, August 2017. SYSBM 001641-1644, 4 females (20.5 × 16.0 mm, 15.1 × 11.8 mm, 14.1 × 10.8 mm, 12.3 × 10.0 mm), same as SYSBM 001640. ZRC, 1 male (19.7 × 15.4 mm), Coloane, Macau, small hillstream, under rocks, coll. C. Huang, January 2018. ZRC, female (16.7 × 13.2 mm), same data as above. AM P101300, male (19.0 × 15.4 mm), Coloane, Macau, small hillstream, under rocks, coll. C. Huang, February 2018.

Distribution.

Hengqin Island, Zhuhai, Guangdong; Coloane, Macau.

Conservation status.

Cantopotamon hengqinense was previously only known from three hill streams in Dahengqin Mountain in Hengqin Island. This study found it to be present in another three hill streams in the neighbouring southwest corner of Coloane, Macau, which extends its extent of occurrence to 34.6 km2 (excluding sea area), area of occupancy to 11.7 km2 and number of locations to two. The populations in Hengqin and Macau are currently isolated from each other by a narrow strip of sea. Unlike the Hengqin population, whose habitat is threatened by urban development ( Huang et al. 2017), the Macau population does not face serious imminent threat as all localities at which it was found are not currently open to development. Specimens from Macau are morphologically indistinguishable from those found in Hengqin Island. Cantopotamon hengqinense has not been found in Xiangzhou, Zhuhai to the north and Sanzao Island to the west despite considerable survey efforts during 2011-2018. In fact, no species of Cantopotamon are known from Sanzao Island, where instead Cryptopotamon anacoluthon (Kemp, 1918) is abundant. Given that the extent of occurrence and area of occupancy of C. hengqinense is much lower than 5, 000 km2 and 5000 km2, respectively, with fewer than five known locations and projected decline in habitat quality in Hengqin, the suggested corresponding conservation status of this species under IUCN Red List criteria remains as indicated by Huang et al. (2017), as Endangered B2(a)(b).